This invention relates to filter cigarettes. More particularly, the present invention relates to filter cigarettes which are adjustable by the smoker to vary the air dilution value.
It is known to produce variable dilution cigarettes having integral rotatable elements for controlling dilution. The rotatable element can be a rotatable band of tipping paper retained by stationary bands against axial displacement and having a slit overlying a slit in the filter plug wrap with which it can be rotated into and out of registry. Alternatively, it can be a rotatable section of the filter plug, carrying with it a section of tipping paper extending over a stationary section of the filter plug. The extending section of the tipping paper has a slit which overlies a slit in the plug wrap on the stationary filter plug segment. The slits can be moved in and out of registry by rotating the rotatable filter segment. Such a cigarette is described in commonly-assigned U.S. Pat. No. 4,532,943, which is hereby incorporated by reference in its entirety.
In the manufacture of these types of cigarettes, the slits in the tipping paper and plug wrap are most easily formed by simultaneously slitting both layers with a knife or laser beam mounted on the cigarette making machine. The cigarettes are therefore assembled initially with the slits fully in registry both longitudinally and rotationally. The dilution level can then be adjusted by rotating the rotatable segment, varying the rotational registry of the slits.
In such a cigarette, it is intended that the longitudinal registry of the slits not change as the filter segments are rotated. However, with certain constructions, rotation of the rotatable segment may cause longitudinal motion of the rotatable segment, affecting the longitudinal registry of the slits and impairing control of the dilution level.
Also in such a cigarette, the resistance-to-draw of the cigarette decreases as dilution increases, unless additional elements are incorporated into the cigarette, as described in said above-incorporated application.
It would be desirable to be able to provide a variable dilution cigarette of the type described above, and a method of manufacture thereof, in which the slits can be formed in the tipping paper before the cigarette is assembled, so that the cigarette making machine need not include a knife or a laser beam.
It would also be desirable to be able to provide a variable dilution cigarette of the type described above, and a method of manufacture thereof, in which the resistance-to-draw remains more nearly constant as dilution is varied, without the incorporation of additional elements in the cigarette.
It would also be desirable to be able to provide a variable dilution cigarette of the type described above, and a method of manufacture thereof, in which a change in the longitudinal registry of the slits does not affect control of the variable dilution feature.